His family confirmed his death on Friday after volunteer divers with the Florida fire department located his body.

The 37-year-old Canadian's family said they were "absolutely heartbroken" and told the Toronto Star he was found "peacefully in the ocean".

His family added: "We are so deeply grateful to everyone who helped with the search and find comfort that Rob passed doing what he loved. We are working on how best to honour his incredible work and my family asks that everyone give us some private time to grieve."

According to The Huffington Post Canada, U.S. Coast Guard said his body was discovered 90 metres from where Stewart was last seen.

He was last seen on Tuesday when he had just returned to the surface after a dive about 70 metres down near Alligator Reef in the Florida Keys.

Stewart's diving partner had lost consciousness as he got into the dive boat.

Coast guard Captain Jeffrey Janszen said as others tended to that man and gave him oxygen, Stewart disappeared and his family believes he may have also lost consciousness.

His mentor, anti-poaching activist Captain Paul Watson, paid tribute to him on Facebook: "He accomplished so much in his 37 years. The films Sharkwater and Revolution and all the work he has been doing for Sharkwater Two - Extinction.

"A courageous and talented man of passion. He knew the risks involved with his work and told me once that sharks were the least of those risks.

"We will miss him and we intend to honour his life by working to protect and defend the sharks that he loved so much."